diff --git a/js/message.js b/js/message.js
index 5ca0a73..aa6e157 100644
--- a/js/message.js
+++ b/js/message.js
@@ -172,7 +172,8 @@
  *     dead code eliminate fields used in protocol buffers that are never used
  *     in an application.
  */
-goog.define('jspb.Message.GENERATE_TO_OBJECT', true);
+jspb.Message.GENERATE_TO_OBJECT =
+    goog.define('jspb.Message.GENERATE_TO_OBJECT', true);
 
 
 /**
@@ -184,7 +185,8 @@
  *     used in an application.
  *     By default this is enabled for test code only.
  */
-goog.define('jspb.Message.GENERATE_FROM_OBJECT', !goog.DISALLOW_TEST_ONLY_CODE);
+jspb.Message.GENERATE_FROM_OBJECT = goog.define(
+    'jspb.Message.GENERATE_FROM_OBJECT', !goog.DISALLOW_TEST_ONLY_CODE);
 
 
 /**
@@ -192,7 +194,8 @@
  *     this off if you do not use toString in your project and want to trim it
  *     from the compiled JS.
  */
-goog.define('jspb.Message.GENERATE_TO_STRING', true);
+jspb.Message.GENERATE_TO_STRING =
+    goog.define('jspb.Message.GENERATE_TO_STRING', true);
 
 
 /**
@@ -200,7 +203,8 @@
  *     local (e.g. not from another iframe) and thus safely classified with
  *     instanceof Array.
  */
-goog.define('jspb.Message.ASSUME_LOCAL_ARRAYS', false);
+jspb.Message.ASSUME_LOCAL_ARRAYS =
+    goog.define('jspb.Message.ASSUME_LOCAL_ARRAYS', false);
 
 
 // TODO(jakubvrana): Turn this off by default.
@@ -210,7 +214,8 @@
  *     the proto before serialization. This is enabled by default to be
  *     backwards compatible. Projects are advised to turn this flag always off.
  */
-goog.define('jspb.Message.SERIALIZE_EMPTY_TRAILING_FIELDS', true);
+jspb.Message.SERIALIZE_EMPTY_TRAILING_FIELDS =
+    goog.define('jspb.Message.SERIALIZE_EMPTY_TRAILING_FIELDS', true);
 
 
 /**
@@ -326,6 +331,10 @@
   return fieldNumber + msg.arrayIndexOffset_;
 };
 
+// This is only here to ensure we are not back sliding on ES6 requiements for
+// protos in g3.
+jspb.Message.hiddenES6Property_ = class {};
+
 
 /**
  * Returns the tag number based on the index in msg.array.